This invention relates to processes for epoxidizing diene-containing polymers and removing hydrogenation catalyst residue therefrom. More specifically, the present invention relates to a process for the concurrent epoxidation of, and hydrogenation catalyst residue extraction from, anionically polymerized diene-containing polymers which have been partially hydrogenated.
The hydrogenation or selective hydrogenation of conjugated diene polymers has been accomplished using any of the several hydrogenation processes known in the prior art. For example, the hydrogenation has been accomplished using methods such as those taught, for example, in U.S. Pat. Nos. 3,494,942; 3,634,594; 3,670,054; 3,700,633 and Re. 27,145, the disclosure of which patents are incorporated herein by reference. These methods known in the prior art for hydrogenating polymers containing ethylenic unsaturation and for hydrogenating or selectively hydrogenating polymers containing aromatic and ethylenic unsaturation, involve the use of a suitable catalyst, particularly a catalyst or catalyst precursor comprising a Group VIII metal.
In the method described in the foregoing patents, a catalyst is prepared by combining a Group VIII metal, particularly nickel or cobalt, compound with a suitable reducing agent such as an aluminum alkyl. Also, while aluminum alkyls are the preferred reducing agents, it is known in the prior art that alkyls and hydrides of metals of Groups I-A, II-A and III-B of the Periodic Table of the Elements are effective reducing agents, particularly lithium, magnesium and aluminum. In general, the Group VIII metal compound is combined with Group I-A, II-A or III-B metal alkyl or hydride at a concentration sufficient to provide Group I-A, II-A and/or III-B metal to Group VIII metal ratios within the range from bout 0.1/1 to about 20/1, preferably from about 1/1 to about 10/1. As indicated in the foregoing patents, the hydrogenation catalyst is generally prepared by combining the Group VIII metal compound and the reducing agent in a suitable solvent or diluent at a temperature within the range from about 20.degree. C. to about 60.degree. C. before the catalyst is fed to the hydrogenation reactor.
Epoxidation of diene-containing polymers is known and it is known that epoxidation can be effected by generally known methods such as by reaction with organic peracids which can be preformed or formed in situ. Suitable known preformed peracids include but are not limited to peracetic, performic, and peroxybenzoic acids. Epoxidation may also be accomplished by treatment of the polymer with hydroperoxides in the presence of transition metals such as Mo, W, Cr, V, Mn, and Ag. Epoxy functionality may also be created by direct oxidation of ethylenic unsaturation by O.sub.2 in the presence of tetra cyanoethylene.
Heretofore, the two process steps of catalyst removal and epoxidation have been carried out as separate reaction steps and in separate reaction vessels. The reasons why these two process steps have been separate are (1) they are typically performed sequentially and (2) they have required different raw materials and process conditions. It would be highly advantageous to provide a process wherein these two steps were combined so that the same reactor could be used, the raw materials, i.e., solvent and oxidizing agents, epoxidizing agents and neutralization agents, usage could be reduced, and that overall batch cycle time and process equipment could be reduced. The present invention provides a process which gives these advantages.